[PATCH] pgarchives: bugfix: increase listsubscription username length

The listsubscription username field is populated by pglister_sync,
copying information from auth_user.email, which can be up to
254 characters.
If a user defined an email address that is longer than 30
characters, pglister_sync will crash:

Traceback (most recent call last):
File "/path/pglister_sync.py", line 83, in <module>
curs.execute("WITH t(u) AS (SELECT UNNEST(%(usernames)s::text[])), ins(un) AS (INSERT INTO listsubscribers (username, list_id) SELECT u, %(listid)s FROM t WHERE NOT EXISTS (SELECT 1 FROM listsubscribers WHERE username=u AND list_id=%(listid)s) RETURNING username), del(un) AS (DELETE FROM listsubscribers WHERE list_id=%(listid)s AND NOT EXISTS (SELECT 1 FROM t WHERE u=username) RETURNING username) SELECT 'ins',un FROM ins UNION ALL SELECT 'del',un FROM del ORDER BY 1,2", {
psycopg2.errors.StringDataRightTruncation: value too long for type character varying(30)

This patch fixes the issue by using the same max length as any
django email field for this field.
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Célestin Matte